It'll almost certainly have seized due to running too lean (not enough fuel in the air/fuel mixture), bearing in mind by doing the wire splice you added the potential for about another 30% of power not checking it didn't want a tad more fuel may have been a little presumptuous.

I also note you get fuels with some pretty low RON ratings over there, if you're using anything under 95 RON then don't read too much into anything anyone English says about jetting.
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